Injuries to ligaments are commonly treated using surgical procedures that involve forming a bone tunnel and placing a replacement graft in the tunnel. For example, treatment of a damaged anterior cruciate ligament (ACL) in a knee can include placing a replacement graft through a tunnel prepared in a femur. The tunnel is typically prepared in the femur from a position at or near the trochlear notch up through a portion of the femur and exiting through a side of the femur at a superior location. A graft is typically looped over a loop attached to a button. The button is able to pass in one direction up through the tunnel and then out adjacent a superior end of the tunnel. The button is typically reoriented such that it will not pass back through the tunnel and is typically positioned against the femur with the loop and graft hanging down into the tunnel therefrom. The tunnel has sufficient diameter at its inferior portion to accommodate the graft. The tunnel is typically made narrower at the superior portion, which carries only the loop and not the graft, to minimize bone removal.
Determining a proper depth of the inferior portion of the tunnel, and consequently also determining a proper size of the graft to position therein, quickly, accurately, and easily can be difficult because the inferior portion of the tunnel is “hidden” within the femur. Typically, a surgeon must use a total length of bone stock and preferred length of graft in tunnel to arrive at which loop length button to pick and at least how far to drill the femoral socket. However, these rely on estimations, and these determinations take time during the surgical procedure. The surgical procedure thus stalls until the correct calculations and determinations are made. Additionally, inadvertent mathematical errors can occur in calculating a minimum depth of the femoral socket and/or determining the loop size, which can further prolong the length of the surgical procedure.
Accordingly, there remains a need for improved methods, systems, and devices for gauging a bone tunnel.